According to kind of ejected fluid, a gas and liquid knife could be divided into two kinds, i.e., gas knife and liquid knife. The gas knife is generally used to cut off liquid via gas flow; while the liquid knife is generally used to pre-wet product by ejecting liquid.
A gas and liquid knife according to prior art, as shown in FIG. 1, includes a chamber 01 and two knife lips 02 and 03 extending from the chamber 01. The two knife lips 02 and 03 are sheets parallel with each other. A gap x between the two knife lips communicates with internal of the chamber. One end of the gap away from the chamber forms an ejection opening k. An inlet 04 is formed at the chamber 01. Gas or liquid at high speed runs into the chamber 01 via the inlet 04 and then ejects out via the ejection opening k. During ejection, the gas or liquid will be restricted by the knife lips 02 and 03 so as to eject in one direction. A distance between the knife lips 02 and 03 is a width of the ejection opening k, which generally could be reduced by adhering shim at inner side of the knife lip 02 or knife lip 03.